Vehicle headlamp with improved filament mounting structure



R. N. FALGE March 21, 1967 VEHICLE HEADLAMP WITH IMPROVED FILAMENTMOUNTING STRUCTURE Filed June 14, 1965 United States Patent 3,310,702VEHICLE HEADLAMP WITH IMPROVED FILAMENT MOUNTING STRUCTURE Robert N.Falge, RR. 2, Box 305, Anderson, Ind. 46011 Filed June 14, 1965, Ser.No. 463,608 3 Claims. (Cl. 313113) The subject matter of the presentinvention is an improved lamp and more particularly an improvedfilamentlead structure for sealed beam lamps of the type used forheadlamps in automotive vehicles.

The conventional lighting element structure in sealed beam automotivevehicle headlamps consists of a generally U-shaped tungsten filamenthaving a coil portion which forms the bottom of the U and an integralleg portion extending from each end of the coil. The filament legs aresecured by staking, welding or both, to the ends of straight lead wires,the filament legs being generally parallel to each other and formingextensions of the generally parallel ends of the two lead wires.

The present invention provides an improvement in such structure and hasas its principal object the provision of a filament-to-lead structurefor vehicle headlamps and the like which assures better and more uniformheadlamp quality, longer headlamp life and improved lightingcharacteristics and efficiency. More specifically, it is an object ofthe invention to provide a lamp having a filament-tolead structure whichavoids mounting strains at the filament-to-lead joints thereby improvingelectrical connections between filament and leads and avoiding coildistortion and coil mislocation due to mounting strains.

Briefly, these objects are accomplished in accordance with the inventionby a filament having a coil portion with an integral leg at one endthereof extending at an angle to the longitudinal axis of the coilportion and secured to the end of one lead wire, and an integral legextending from the other end of the coil generally parallel tolongitudinal axis of the coil and secured to the end of the other leadwire. Preferably the end of the lead wire to which the second-mentionedfilament leg is secured extends transversely to the optical axis of thelamp and at about right angles to the end of the other lead wire suchthat each filament leg is coaxial with the end of the lead wire to whichit is secured. One of the chief advantages of such structure is that itgreatly reduces the tendency of the filament legs to separate from theleads due to strains generated in the junctions during lamp manufactureor during lamp operation. With conventional filament structure, forexample, due to manufacturing inaccuracies in forming the filaments itfrequently occurs that the two legs instead of extending parallel toeach other, as is necessary to provide an unstrained condition when thelegs are initially secured to the leads, the legs in fact are at anangle to each other about the longitudinal axis of the coil. Hence, whenthe legs are secured to the leads in lamp manufacture, there isimmediately a strain tending to cause the legs to pull free of theleads. Also, since the leads are fixed the result is that the filamentcoil twists and moves thereby destroying the accurate filament locationprovided by fixtures in the mounting operation. To prevent such acondition of initial strain it is essential, with the conventionalfilament-to-lead structure, to use and precisely attain fully completecoil turns in the filament coiling operation in order to provide preciseparallelism between the legs. Such precision is difiicult to attain inthe coiling operation and where it is not attained it leaves a choice ofeither scrapping those filaments which have partial turns and hence lackthe desired leg parallelism or using such filaments with resultantinferiority .due to strains in the lamp filament-tolead joints. With thestructure of the present invention, since one filament leg extends fromone end of the coil coaxially With the longitudinal axis of the coil,its precise angular orientation with respect to the coil and withrespect to the other filament leg will be the same irrespective ofWhether there are partial turns imparted to the coil in the coilingoperation. Hence, the possibilities of the legs being in an initiallystrained condition during lamp manufacture are minimized. Further, asthe coil heats during lamp operation there is minimum tendency for thelegs to change their orientation with respect to each other and henceminimum strain on the leg-to-lead joints.

Other objects, advantages and features of the invention will be apparentfrom the following detailed description of a preferred embodimentthereof made With reference to the accompanying drawings in which:

FIGURE 1 is a side view, with parts broken away, of a sealed beamheadlamp embodying the invention;

FIGURE 2 is a top view in enlarged scale of one of the filament-to-leadelements of the lamp shown in FIG- URE l; and

FIGURE 3 is a partial perspective view in enlarged scale of the lampshown in FIGURE 1 and shows the filament-to-lead structure.

Referring now to the drawings, there is shown an auto motive vehiclesealed beam headlamp having a conventional hermetically sealed glassenvelope including a glass parabolic reflector 2 which has an aluminizedfront surface 4 (see FIGURE 3) and which is sealed by fusion at itsperiphery 6 to a glass lens 8 having the desired flutes and prisms (notshown) on the inner surface thereof to provide the desired beam pattern.Extending into the lamp through the reflector in sealed relationshiptherewith are three lead wires 10, 12 and 14, each having its ownelectrical connector exterior of the reflector as shown for example at16. The lead wire 12 has a lead wire 18 welded thereto within the lamp,wires 10 and 12 being for one filament and wires 14 and 18 being for theother filament. This structure which is shown is, of course, for a lamphaving a high beam filament and a low beam filament, it being understoodthat the invention is also applicable to a one filament type lamp inwhich instance only two lead wires are required. Also, it will beunderstood that the precise arrangement of the lead wires as they enterthe glass envelope and the shape of the lead wires remote from the freeends thereof can vary from what is shown. In some instances, forexample, the lead structure adjacent the envelope is modified to supporta filament cap or shield positioned in front of the filaments and suchcan, if desired, be used with the present invention.

Referring now to the spaced pair of lead wires 10 and 12, the latter hasan end portion 20 which extends parallel to the optical axis of the lamp(i.e., the axis which extends through the focal point of the reflectorparallel to the light rays from the reflector) and the wire 10 has anend portion 22 which is bent to extend in a direction transverse to theoptical axis of the lamp and hence at about a right angle to the endportion 20 of the other lead wire 12. Bridging these two leads is atungsten filament 24 having an elongated coil portion 26 which extendstransversely to the optical axis of the lamp' and which has integrallegs 28 and 30 extending from the ends thereof. Filament leg 28 extendsfrom the coil at a right angle to the longitudinal axis of the coil andis secured by staking or welding to the end 20 of the lead wire 12, theleg 28 being positioned coaxially with the lead wire end portion 20. Theother leg of the filament, leg 30, is staked or welded into andcoaxially with the end portion 22 of the lead wire 10.

Filament 32 which is substantially the same as filament 24 is securedacross leads l4 and 16 in the same manner.

It will be noted that with the structure shown the angular orientationof the filament leg 30 with respect to the leg 28 is not dependent uponthe turns in the filament coil portion 26; leg 30 will always extend atthe same angle with respect to leg 28. Hence, the structure showngreatly increases lamp durability with lessened possibilities ofdisconnection of the filament to one of the leads. Additionally, thefilament-to-lead structure shown and described improves the efficiencyand lighting characteristics particularly of the low or city drivingbeam. The low beam hot spot is made up of filament images from thereflector transmitted through the lens. The best images for optimizingthe low beam are those in and near the vertical plane through thereflector which bisects the low beam filament transversely through itslongitudinal axis. The filament legs of the convention U-shaped filamentare directed upward from the upper half of the reflector and areincandescent in decreasing degree from the coil to the lead wire therebytending to dull the low beam cut off. With the improved filamentstructure of the present invention wherein the right leg is coaxial withthe filament coil, this dulling of the beam cut off is eliminated on theleft side and the stray light is directed to the left instead of upward.Further, by using a short coaxial filament leg as shown at 30, theextent to which the stray light is directed to the left can be kept to aminimum. Also, by suing the short coaxial filament leg 30, as shown,eificiency is increased since less heat is dissipated through the shortleg.

As alluded to above, the invention reduces the need for precision in thecoiling of the filaments in order to attain optimum lamp durability andlighting characteristics. Hence, there need be little scrap loss in thefilament coiling operation. Since a filament-to-lead strain conditionwill not result from slight inaccuracies in the coiling operation, it isnot necessary to set the filament wire so much in the winding and thisin turn permits the use of a larger mandrel with fewer turns. Springbackin the cooling operation is less a problem.

For optimum efiiciency and lighting characteristics, the filament mustbe precisely located on the focal point of the parabolic reflector. Ofcourse on a two filament lamp as shown, only one filament can be solocated. In a two headlamp vehicle lighting system the high beamfilament is located on the focal point. For a four lamp system as is nowcommonly used, the low beam filaments of one pair of lamps is located onfocus and the single high beam filament of the other pair of lamps islocated on focus. In either case, however, it is always desirable tohave one filament or the other precisely located on the focal point.With the conventional U-shaped filament, strains resulting from filamentheating have a tendency to twist the filament off focus. Such twistingalso causes the turns of the coil to change pitch; the turns which areclosed up and brought closer together have an increased tendency tooverheat and reduce the life of the unit, and the turns which arestretched will operate at lower temperature with resultant reduced lightoutput. With the structure of the present invention there is lessertendency for the filament coil to undergo such twisting due to strainsthereby better assuring that the filament remains on focus and providesoptimum lighting performance and durability. Further, the inventionaffords greater discretion in filament design since with the oldU-shaped filament structure an even number of coil turns was necessaryto attain the required parallelism between filament legs whereas withthe present structure partial coil turns can be used if desired withouteffect on the orientation of one filament leg to the other.

Whereas in the two-filament lamp structure shown in the drawings, thebent leads 10 and 14 are both located on the same side of the lamp, itmay be desirable to locate the bent lead for one filament on one sideand the bent lead for the other filament on the other side as, for example, by reversing the locations of leads 10 and 12 for filament 26.

It will be understood therefore that whereas the invention has beendescribed in detail with reference to a particular embodiment thereof,various changes and modifications may be made all within the full andintended scope of the claims which follow.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A vehicle headlamp comprising; an envelope having a reflector and alens, an electrical lead wire in said envelope having an end portionextending parallel to the optical axis of the lamp, an electrical leadwire in said envelope having an end portion extending transversely tothe optical axis of the lamp, and a filament having a coil with a legextending from one end thereof at an angle to the axis of said coil andsecured to the end portion of said first-mentioned lead wire and with aleg extending parallel to the axis of said coil and secured to the endportion of said second-mentioned lead wire the axis of said coilextending transversely to the optical axis of said headlamp adjacent thefocal point thereof.

2. A vehicle headlamp as set forth in claim 1 wherein the length of saidsecond-mentioned leg between the end of said first-mentioned lead andsaid coil is shorter than the length of said first-mentioned leg betweenthe end of said second-mentioned lead and said coil.

3. A vehicle headlamp comprising; an envelope having a reflector and alens, a pair of spaced lead wires extending into said envelope throughsaid reflector and having straight free end portions positioned at aright angle to each other, and a filament having an elongated coil witha leg extending from one end thereof at a right angle to the axis ofsaid coil and secured to the end portion of one of said lead wirescoaxially therewith and a leg extending from the other end of said coilcoaxially with said coil and secured to the end portion of the other ofsaid lead wires coaxially therewith, the axis of said coil extendingtransversely to the optical axis of said headlamp adjacent the focalpoint thereof.

References Cited by the Examiner UNITED STATES PATENTS 1,121,802 12/1914Clark 316-4 2,131,897 10/1938 Malter 3l3272 2,359,302 10/1944 Curtis2925.l5

2,795,722 6/1957 Burgener et al. 313-117 JAMES W. LAWRENCE, PrimaryExaminer.

v, LAFRANCHI, Assistant Examiner,

1. A VEHICLE HEADLAMP COMPRISING; AN ENVELOPE HAVING A REFLECTOR AND ALENS, AN ELECTRICAL LEAD WIRE IN SAID ENVELOPE HAVING AN END PORTIONEXTENDING PARALLEL TO THE OPTICAL AXIS OF THE LAMP, AN ELECTRICAL LEADWIRE IN SAID ENVELOPE HAVING AN END PORTION EXTENDING TRANSVERSELY TOTHE OPTICAL AXIS OF THE LAMP, AND A FILAMENT HAVING A COIL WITH A LEGEXTENDING FROM ONE END THEREOF AT AN ANGLE TO THE AXIS OF SAID COIL ANDSECURED TO THE END PORTION OF SAID FIRST-MENTIONED LEAD WIRE AND WITH ALEG EXTENDING PARALLEL TO THE AXIS OF SAID COIL AND SECURED TO THE ENDPORTION OF SAID SECOND-MENTIONED LEAD WIRE THE AXIS OF SAID COILEXTENDING TRANSVERSELY TO THE OPTICAL AXIS OF SAID HEADLAMP ADJACENT THEFOCAL POINT THEREOF.